Repeating electric fuse



A 10,1948. J, BRYAN 2,446,739

REPEATING ELECTRIC FUSE Filed Oct. 24, 1947 INVENTOR. John 14 dr'yan Afor/rays I Patented Aug, 10, 1948 UNITED sTATEs PATENT OFFICE REPEATINGELECTRIC FUSE John W. Bryan, Traphill, N. C.

Application October 24, 1947, Serial No. 781,862

1 Claim. (01. 200-426) This invention relates generally to improvementsin thermal circuit breaking devices in which any desired number of fuseelements may be connected in successive order into a protected circuitwithout the attention of an attendant.

One of the objects of the invention is to provide an arrangement inwhich an electrical circuit is broken wherever a pulse of currenttherein exceeds a predetermined value.

Another object is to provide means for successivelyand automaticallyconnecting into the circuit a new fuse element whenever the precedingelement has been burned out.

A further object is the provision of a repeating fuse structure which isinexpensive, easy to manufacture and which is adapted to convenientreplacement of inexpensive fuse elements already expended.

Further objects and advantages will be apparent from the description andaccompanying drawings, in which:

Figure 1 is a plan view of the repeating electrical fuse.

Figure 2 is a side elevation of the fuse of Figure 1.

Figure 3 is a cross-section of the central portion of the fuse takenalong line 3-4 of Figure l.

Figure 4 is anenlarged view of a fuse element suitable for use with thestructure of Figure 1.

The repeating fuse is conveniently constructed on a base I I ofinsulating material but from sheet stock or molded to the desired form.A pair of metallic discs 12 are fastened to the sides, respectively, ofthe base H by means of a bolt I4 passing through the center of the base,and secured by the nut i5. Electrically and mechanically connected tothe discs 12 are a suitable number of studs l6 which project slightly,from the discs and are preferably provided with notches or heads toreceive and hold in place a wire loop [9 of a fuse element IS. The loopsI! are of sufiicient size to slip over the heads of the studs thusfacilitating installation or removal of the fuse elements. The fuseelement is constructed of material having electrical and mechanicalcharacteristics selected to burn out at a predetermined current load.The loops is are formed from the fusible material of the fuse elementitself thus reducing cost of manufacture and assuring uniformity.

Terminal studs I! are preferably secured to the base by a punching orpressing operation, which also secures one end, respectively, of thecontact springs 20 to the base in fixed orientation thereto. The studsIl may be provided with square shanks or keys for the purpose ofmaintaining the orientation of the spring such that when the free endthereof is released by the breaking or burning of the fuse element thespring unfiexes and moves 7 studs H. The ends of the springs and thestuds 7 may be silvered or otherwise plated if desired to improvecontact for low voltage applications.

As shown in Figure 1, the fuse element has one.

loop slipped over a stud l6 and the other loop in electrical contactwith the flexed spring 20 by way of the hook 26. The tension of theflexed spring maintains good electrical contact from stud ll via spring20, book 26, fuse element 18 to stud I6.

Any circuit to be protected by the fuse may be connected thereto by wayof a lead 2|, lug 23, a first stud II, a first spring 20 and hook 26, afirst fuse element iii, a first stud l6, plate l2, center bolt 14, 9.lug 22 secured to the central bolt, and thence to the return lead of theprotected circuit.

The springs 20 are of a length suitable to span the space betweensuccessive studs ll and contact is maintained between the center boltand the lug 2| wherein one fuse element connects a spring with acorresponding stud I6. Contact between the first stud l1 and successivestuds ll by way of corresponding springs 20 is maintained except where afuse element holds the corresponding spring away from contact with thenext succeeding stud ll.

The last spring in the series, taken clockwise in Figure 1, is providedwith a pin 24 and a bridging bar 25 pivoted on the pin 24. This bar isof suitable length to bridge the first stud ll With an auxiliary stud 21which is mounted-in the base II. A second repeating fuse assembly may beelectrically connected to the first by interconnecting the center boltsthereof and the stud 21 of the first assembly to the first stud ll ofthe second assembly. Two assemblies may be placed on the same base, asshown in Figures 1 and 2. Also a number of units may be assembled on asingle interconnecting center bolt and the first studs ll of the variousunits electrically connected to studs 21 of preceding units. In thismanner any desired number of fuse elements may be assembled in aninterconnected group of assemblies, and each element is thus connectedinto the protected circuit in succession as the preceding element breaksthe circuit.

When the desired number of protecting fuse elements are assembled, asdescribed, the operation of the repeating fuse is as follows:

The current in the protected circuit enter and .aves the fuse assemblyby leads 2! and 22, the current passing through the first spring andfuse element. When a surge of current of sum- 7 cient strength occursthe first fuse element is heated to the fusing temperature, therebybreaking the element and the conducting spring is released. The firstspring thereupon snaps over to the second stud I1 and connects thesecond spring and fuse element into the protected circuit by way ofthesecond stud I1, second fuse l8 and the center bolt I4. Any further surgeof current of greater than predetermined value causes the second fuseelement to burn out and the second spring to make contact with the thirdspring by way of the third stud II. This action repeats as often asdangerous current surges occur and as long as a fuse element remains onone of the interconnected assemblies. No attendant is required over longperiods of time, and the protected circuit is restored quickly aftereach such current surge without appreciable loss of service. Theattendant for equipment employing this improved fuse system may,therefore, by periodic inspection of the fuse assemblies, maintaincontinuous service. Any burned out elements are readily replaced withoutdisturbing the assembly or the assembly may be quickly removed andreplaced if desired.

If it is desired to delay the resumption of service by holding thecircuit open for a time after each short circuit or current surge forany desired period in each instance this may be done by employing amechanical delay element of conventional design to prevent immediatemovement of spring 20 from its fiexed position into contact positionagainst the next stud H. For this purpose a dash pot may be employed toslow the motion of the spring or an escapement mechanism may beconnected to accomplish a longer delay in the motion of the spring.

Various changes may be made in thedesign and manufacture of therepeating fuse without 4 departing from the spirit of the presentinvention.

What is claimed is: An automatic multiple fuse comprising an insulatedbase plate, a centralized terminal plate fixed on said base plate, aseries of circumferentially spaced studs projecting therefrom, a se--ries of circumferentially spaced contacts projecting from saidbase'plate surrounding said terminal plate in concentrically spacedrelation-to said terminal plate, a scrim of conductive leaf springssecured at one end to said contacts and free at their opposite ends,said leaf springs being outwardly tensioned to electrically engage theirfree ends with circumferentially adjacent ones of said contacts whenreleased so as to bridge adjacent contacts, and fusible elementsstretched between said studs and the free ends I of related leaf springswhereby said leaf springs are deflected inwardly and tensioned out ofengagement with the contacts related thereto, whereby fusing of one ofsaid fusible elements permits the leaf spring related thereto to springoutwardly and engage the circumferentially adjacent contact and therebyrestore a circuit in which said terminal plate and said studs areconnected, 9. second series of similar studs, contacts, fusibleelements, and leaf springs on the opposite side of said base plate, anintermediate contact between two of adjacent contacts ofthe first seriesand electrically connected to a contact of the second series, and abridging element carried by one of the leaf springs of the first seriesin position to bridge said intermediate contact and an adjacent contactof the first series whenever the last of the first series fusibleelements is fused and the related leaf spring is released to engage suchadjacent first series contact, whereby the circuit is restored by thefirst fusible element of the second series thereof.

J OHN W. BRYAN.

REEERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

